During ophthalmic and Head and Neck surgery, a sterile surgical field is required to prevent infection. In ophthalmic surgery, the patient's entire head and body are covered by the sterile drapes. These drapes are usually composed of a combination of cotton or synthetic fabric combined with plastic. The plastic drape usually covers the patient's entire face (example 3-M Corporation 10-60 drape). Other drapes cover the entire head and face with synthetic fiber cloth with plastic covering only the operated eye. Both types of drapes cover the entire face. The drapes are form-fitting and are applied around the operated eye with adhesive. This causes the drape to come in contact with the patient's face nearly 100% of the time.
More than 95% of ophthalmic surgical procedures are performed under local anesthesia. The patient is given topical or injectable anesthesia around the eye. The patient is rarely put to sleep with general endotracheal intubation. Many patients are given intravenous medications for sedation and comfort. Patients who are awake during their surgery may experience feelings of claustrophobia from lying under the plastic drapes closely adherent to the eye, nose and mouth. In addition, the exhalation under a form fitting plastic drape can make a patient feel warm, sweaty and uncomfortable. As the perspiration and temperature rises, it can make the patient feel anxious, contributing to a further sense of claustrophobia and panic.
Carbon dioxide (CO.sub.2) is a prominent component of exhaled air. When a patient is under sterile drapes during surgery, exhaled air and supplemental oxygen can be trapped under form-fitting drapes. As a result, it is possible that both CO.sub.2 and oxygen levels may rise as air is trapped under the form-fitted drapes. Patients are usually given supplemental oxygen through a nasal cannula or mask under the drapes. This helps to prevent hypoxia (low oxygen blood levels). It does not, however, prevent the slow build up of carbon dioxide under the drape, which can lead to hypercarbia.
Hypercarbia is a potentially dangerous condition that occurs when carbon dioxide levels rise in the blood stream. It can occur from breathing higher levels of carbon dioxide. A person suffering from early hypercarbia may respond in an agitated or combative manner. This is a major concern during long and delicate procedures. Ophthalmic surgical procedures performed under local anesthesia necessitate the patient to lay still for upwards of two hours or more. A patient can easily become agitated during the surgery if he becomes claustrophobic or uncomfortably warm or sweaty as a result of exhaled air trapped under the drape. If carbon dioxide levels rise, leading to hypercarbia, this can make a borderline situation worse. An agitated patient may require deeper sedation to keep him calm. This additional anesthesia, in some cases, may provide the effect opposite than that intended by increasing and exacerbating hypercarbia. Even if it does not worsen the hypercarbia, the extra sedation can increase the risks to the patient and increase the amount of time that the patient spends recovering from the effects of anesthesia.
Form-fitting surgical drapes used in head, neck and ophthalmic surgery tend to increase a patient's discomfort and increase levels of anxiety and claustrophobia. These surgical drapes also allow exhaled air and supplemental oxygen to be trapped under the drapes. This facilitates an increase in temperature, humidity and perspiration under the drapes and contributes to both rising oxygen and CO.sub.2 levels. A number of prior art devices have attempted to address these problems with varying degrees of success.